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Microfiche 

Series. 


CIHM/ICMH 
Collection  de 
microfiches. 


Canadian  Institute  for  Historical  Microreproductions  /  Institut  Canadian  de  microreproductions  historiques 


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7 

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includes  supplementary  material/ 
Comprend  du  materiel  suppl^mentaire 

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Tight  binding  may  cause  shadows  or  distortion 
along  interior  margin/ 

La  reliure  serrie  peut  causer  de  i'ombre  ou  de  la 
distortion  le  long  de  la  marge  intArieure 

Blank  leaves  added  during  restoration  may 
appear  within  the  text.  Whenever  possible,  these 
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II  se  peut  que  certaines  pages  blanches  ajout6es 
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mais.  lorsque  cela  ttait  possible,  ces  pages  n'ont 
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I      I    Only  edition  available/ 


D 


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etc..  ont  6t*  filmAes  h  nouveau  de  fagon  A 
obtenir  la  meilleure  image  possible. 


T 

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This  item  is  filmed  at  the  reduction  ratio  checked  below/ 

Ce  document  est  film*  au  taux  de  reduction  indiqu*  ci-dessous. 

10X  14X  18X  22X 


26X 


30X 


y 


12X 


16X 


20X 


MX 


28X 


32X 


The  copy  filmsd  here  hat  been  reproduced  thanks 
to  the  generosity  of: 

Library  Division 

Provincial  Archives  of  British  Colun.bia 

The  images  appearing  here  are  the  best  quality 
possible  considering  the  condition  and  legibility 
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Original  copies  in  printed  paper  covers  are  filmed 
beginning  with  the  front  cover  and  ending  on 
the  last  page  with  a  printed  or  illustrated  impres- 
sion, or  the  back  cover  when  appropriate.  All 
other  original  copies  are  filmed  beginning  on  the 
first  page  with  a  printed  or  illustrated  impres- 
sion, and  ending  on  the  last  page  with  a  printed 
or  illustrated  impression. 


The  last  recorded  frame  on  each  microfiche 
shall  contain  the  symbol  — ^-  (meaning  "CON- 
TINUED"), or  the  symbol  V  (meaning  "END"), 
whichever  applies. 

Maps,  plates,  charts,  etc.,  may  be  filmed  at 
different  reduction  ratios.  Those  too  large  to  be 
entirely  included  in  one  exposure  are  filmed 
beginning  in  the  upper  left  hand  corner,  left  to 
right  and  top  to  bottom,  as  many  frames  as 
required.  The  following  diagrams  illustrate  the 
method: 


L'exemplaire  film*  fut  reproduit  grAce  A  la 
gtnArositA  de: 

Library  Division 

Provincial  Archives  of  British  Columbia 

Les  images  suivantes  ont  At6  reproduces  avec  le 
plus  grand  soin.  compte  tenu  de  la  condition  et 
de  la  nettetA  de  l'exemplaire  film*,  et  en 
conformity  avec  les  conditions  du  contrat  de 
filmage. 

Les  exemplaires  originaux  dont  la  couverture  en 
papier  est  imprimAe  sont  filmAs  en  commenpant 
par  le  premier  plat  et  en  terminant  soit  par  la 
derniire  page  qui  comporte  une  empreinte 
d'impression  ou  d'illustration,  soit  par  le  second 
plat,  salon  le  cas.  Tous  los  autres  exemplaires 
originaux  sont  filmAs  en  commen^ant  par  la 
premiere  page  qui  comporte  une  empreinte 
d'impression  ou  d'illustration  et  en  terminant  par 
la  derniAre  page  qui  comporte  une  telle 
empreinte. 

Un  des  symboles  suivants  apparaitra  sur  la 
dernidre  image  de  cheque  microfiche,  selon  le 
cas:  le  symbole  -^>  signifie  "A  SUIVRE",  le 
symbole  V  signifie  "FIN". 

Les  cartes,  planches,  tableaux,  etc.,  peuvent  dtre 
film^s  A  des  taux  de  rMuction  diff^rents. 
Lorsque  le  document  est  trop  grand  pour  Atre 
reproduit  en  un  seul  clichi.  il  est  film*  A  partir 
de  Tangle  supArieur  gauche,  de  gauche  d  droite, 
et  de  haut  en  bas,  en  prenant  le  nombre 
d'imagos  n6cessaire.  Les  diagrammes  suivants 
illustrent  la  m^thode. 


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BULLETIN  OF  THE  QEOLOQICAL  SOCIETY  OF  AMERICA 

Vol.  2,  pp.  165-176 


NOTE  ON  THE  GEOLOGICAL  STRUCTURE  OF   THE 
SELKIRK   RANGE 


BY 


GEOIUJE  M.  DAWSON 

ASSISTANT    DIKKCTOK    OF    TIIK   QKOI.OOICAL   8URVBV    OF    CANADA 


KOCH ESTER 

I'UIJLISHED  BY  THE  SOCIETY 

Fbbkuary,  1891 


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BULLETIN   OF  THE   GEOLOGICAL  SOCIETY  OF  AMERICA 
Vol.  2,  pp.  165-176  February  12,  i89i 


J' 


I 


NOTE  ON  THE  GEOLOGICAL   STRUCTURE  OF  THE 
SELKIRK  RANGE. 

EY   GEOKOE    M.    DAW.SON,   ArtSlJSTANT    DIltlXTOK   OF   THK   GEOf.OGIC.Vr, 
.St;UVLY    OF    CAXADA. 

{/{rail  he/ore  the  Sui-icti/  December  29,  ISOO.) 

CONTENTS. 

Page. 

Introduftion 10.5 

Genonil  Feutiiros  of  the  Cordiliorii ]()5 

Surveys  in  the  Interior  PlaU'iui  IJeijioii 106 

Gooloijiciil  Features  of  the  Interior  Pliiteau 107 

Stratigraphy lo7 

The  General  Section  . 107 

The  Shiiswap  .Series 170 

The  Nisconlith  Series 170 

The  Selkirk  Series 171 

General  lielutinns  of  the  Cambrian. ..   . 172 

Newer  liocks ... 174 

Structure .... 174 

Thickness ... 175 

Discussion 170 


Introductiox. 

General  Features  of  the  Cordillera. — Tiie  Cordillera,  or  Rocky  Mountain 
region  of  the  Pacific  coast,  for  a  length  measured  by  seven  degrees  of  lati- 
tude in  the  southern  part  of  tlie  province  of  British  Columbia,  is  narrower 
than  elsewhere,  having  in  this  part  of  its  course  a  widtli  not  much  exceeding 
400  miles.  T!ie  principal  geographical  features  of  this  southern  portion  of 
the  Cordillera  in  British  Columbia  are  now  pretty  well  known,  and  the 
general  geological  outlines  have  also  been  drawn  in,  so  far  as  this  can  be 
done  from  reconnoissance  work.  The  districts  which  have  been  more  closely 
studied  are  few  and  limited  in  size. 

Enough  is  known  to  show  that  this  part  of  the  Cordillera  offers  a  geolog- 
ical problem  of  great  complexity,  such  as  to  require  for  its  solution,  even 

XXV— Hui-L.  Gbou.  Soc.  Am.,  Vol..  2,  1890.  .  (165) 


icr. 


<;.  M.  D.wvsdN-— sTurcTrui;  or  tiik  sKr.KinK  iianok. 


uiKlor  the  most  fiivorable  firciinistiuiccs),  loiij,'  iind  careful  msenrcli.  In  luldi- 
tioii  to  till'  (litticiiltiivs  (if  stniclun'  to  l)e  oxpt'ctcil  in  any  <rrcat  mountain 
system,  spci'ial  diHicultioM  are  found  in  tli«  dej,'ree  to  wliioli  rcj^ional  mctiimor- 
pliism  has  hecn  caniod,  in  the  uccninencc  of  great  volumes  of  contemiiora- 
neous  volcanic  material  at  various  stashes,  and  (partly  no  douht  as  a  conse- 
•lucncc  of  the  last)  in  the  extreme  paucity  of  fossil  renuiins.  Still  further, 
the  circumstance  that  the  region  as  a  whole  must  he  descril)ed  as  more  or 
less  densely  wooded,  contrasts  it  very  unfavoral)ly,  from  a  geologist's  point  of 
view,  with  the  southern  ami  open  parts  of  tlie  t'ordiilera,  where  he  who  runs 
may  reatl  numy  of  the  main  structural  facts. 

Up  to  the  present  time  the  horizons  which  have  in  British  (Johunhia  heen 
actually  fixed  hy  paleontological  evidence  may  be  summarized  as  follows: 

1.  Tertiary  i;^prol)abiy  Miocene). 

2.  Cretac<jous  (various  stages,  probably  extending  from  the  Laramie  as 
far  down  as  the  Neocomian). 

!!.  Alpine  Trias. 

4.  Carboniferous. 

o.  Silurian  {Huh/sllex  beds). 

0.  Cambro-Silurian  (Trenton-Utica  and  perhaps  somewhat  lower). 

7.  Middle  Cambrian. 

8.  Lower  Cambrian  {Okiiellns  beds). 

Of  these  horizons,  all  i)ut  the  Miocene  have  been  recognized  in  the  Rocky 
Mountains  [iroixT,  or  eastern  range  of  the  Cordillera.  On  the  coast  n(.  fos- 
sils definitely  older  than  the  Carboniferous  have  yet  been  detected.  In  the 
interior  plateau,  fossils  referabh;  to  the  Miocene,  lower  Cretaceous,  Alpine 
Trias  and  (Jarboniferous  have  been  rather  sparingly  found,  while  in  the 
mountain  region  of  the  (iold  .system,  including  the  Selkirk,  Purcell,  Colum- 
bia and  other  ranges,  we  are  as  yet  almost  entirely  without  paleontological 
evidence. 

tSiirvei/s  in  the  Interior  Plntenn  lieglnn. — The  writer  has  been  engaged  for 
some  time  in  a  detailed  examination  of  an, area  of  about  (5,400  square  miles  in 
the  interior  plateau  region,  the  nuiterials  for  a  geological  map  of  which  have 
now  been  obtained  and  are  in  course  of  elaboration.  In  connection  with 
this  work,  and  more  particularly  to  assist  in  explaining  the  complexities  of 
the  older  rocks  of  this  area,  it  became  desirable  to  ascertain,  so  far  as  pos- 
sible, the  relations  of  these  rocks  to  those  of  the  Rocky  ^lountains  proper, 
across  which  one  line  of  .section  has  already  been  carefully  worked  out  by 
Mr.  H.  (i.  McCoiinell. 

With  this  object  in  view  a  preliminary  examination  was  nnide  last  autumn 
across  the  intervening  Selkirk  range,  on  the  line  of  the  C'anadian  Pacific 
railway.  This  examination  was  lu'ce.ssarily  confined  to  the  vicinity  of  the 
railway  and  still  reipiires  to  be  supplemented  by  much  detail,  to  be  obtained 


THE   INTKUIOIt    I'l.ATKAf    ItlCfilON'. 


167 


only  by  mountain  clitnl)ing,  and  by  the  study  of  a  belt  of  some  width  on  both 
fides  of  tlie  line.  A.s,  however,  we  have  heretofore  been  almost  without  in- 
fornnition  on  the  geolof,'ical  stnieture  of  the  Helkirks,  it  is  believed  tlnvt  the 
observations  made  may  not  bewitiiout  interest,  even  thonj,'h  j^iven  subject  to 
future  correction  in  detail.  This  ran<re,  where  it  has  been  rendered  easily 
accessible  by  the  construction  of  the  railway,  has  already  become  noted  for 
its  .nagniticent  Alpine  scenery,  wiiile  some  of  its  [xjaks  and  glaciers  have 
become  tlie  subjects  of  serious  ex[)l()ration  by  well-known  Alpine  climbers 
from  England  and  Switzerland.* 

GeoliKjlcal  Features  of  tlie  Interior  Plateau. — In  that  part  of  IJritish  Colum- 
bia wiiich  has  been  called  tlie  interior  plateau  the  oldest  stratified  rocks  are 
gnei.5ses  and  micashists,  which  from  their  lithological  character  are  assumed 
to  represent  the  Archean.  The  relations  of  these  to  the  overlying  Paleozoic 
strata  are  best  known  on  the  ea.stern  bm-der  of  the  plateau  region,  Avhere 
they  are  freijuently  and  well  shown.  Witii  these  crystalline  schists  occur 
certain  old  granitoid  rocks,  which  may  represent  either  portions  of  the  schists 
in  which  the  bedded  structure  has  been  ol)literated  or  very  ancient  intru- 
sions that,  together  with  the  enclosing  crystalline  schists,  have  sub.seipiently 
been  affL'cted  by  heat,  press  ire  and  otiier  agencies.  Besides  these  there  is  in 
the  same  region  at  least  one  later  series  of  distinctly  intrusive  granites,  which 
is  probably  newer  in  date  than  most  of  the  Paleozoic  rocks.  In  the  Coast 
range,  on  the  western  side  of  the  interior  plateau,  a  similar  "complex"  of 
crystalline  schists  and  granites  occurs,  of  whic!)  part  at  least  may  be  of  the 
same  age  with  that  just  alluded  to,  thougli  in  this  ctuse  some  of  the  intrusive 
granites  are  known  to  be  post-Triussie  in  date  and  others  are  later  even  than 
the  Cretaceous. 

STHATIGRAPnY. 

The  General  Section. — The  section  given  in  the  first  column  of  the  annexed 
table  represents  the  rocks  met  with  near  the  eastern  border  of  the  interior 


<  SiU'li  Kf'>>'>Ki<'nl  inilii.'iilioiis  for  tlu'  SelkirUs  «><  Imve  ln'oii  imbl!.'<lie(l  may  V)0  foiitid  In  the  fol- 
lowitif^  vvorky : 

Iti'piiit  on  lli(>  f;eolo){y  of  the  Coiinlry  nenr  tho  K.rlyniiilli  Parallel  of  North  Liitituile,  by  H. 
Baiieriimn.  This  !•<  tht-  r"»iilt  of  ol.scrvmi  >ii!<  minln  in  IS'iii-'ill,  in  I'onnoclion  wllh  the  expeiliiion 
engaKPil  In  lixin;?  Iho  Honlhi'rii  boiimlary  of  Hrilish  t'oliimbia  In  those  years,  but  was  first  publisliecl 
In  the  Hcporl  of  Progress  of  the  (ieolo^ieal  Snrvey  offanada  for  lghi-'S4. 

Siiinniaiy  Koport  of  the  Uperations  of  tile  (ieolonieal  Survey  for  the  year  18.S7,  by  Dr.  A.  R.  C. 
Selwyn.    'i'his  ooniains  a  brief  ncite  on  the  eharaeter  of  the  rocks  riear  Illeeillevvaet. 

Kxplorations  in  the  (ilneier  Uenions  of  the  Selkirk  Range,  Hritish  ("oliimbia,  by  Rev.  W.  Spots- 
w.iod  Green;  Proceerlinxii  of  the  Hoyal  (ieographieal  Sonielv,  vol.  XI,  188'J.  Mr.  lireen  here  gives 
a  short  geolngieal  note  (p.  \(i7)  anil  refers  to  the  diterniination  by  Professor  T.  (J.  Bonney  of  some 
of  the  roeUs  hronght  ba'-l;. 

Notes  on  llie  (ieography  and  Geology  of  the  Hig  Mend  of  the  rolumbia,  bv  Professor  A.  P.  Cole- 
man ;  Tians,  K"yal  Soe.  fan.,  vol.  Vll.seet.  IV.ISW.  In  this  paper  the  general  geologieal  chamcter 
of  disirlels  vi>iled  by  the  anthor  are  deseribed  and  the  results  of  a  petrologionl  examination  of  a 
nnmber  of  roeks  are  given. 

Hrief  mention  has  also  been  made  by  the  writer  of  the  rocks  of  the  '^elklrks  and  neighboring 
ranges  in  l>eserjptlve  >'keteii  of  the  I'liysieal  <»ef)gra()hy  and  Geology  of  the  Dominion  of  Canada, 
IStil :  .Mineral  Wealth  of  Hrillsh  I'olnmbia  (Annnal  Itepofi  Geol.  Snrv.  I'an  .  new  series,  vol.  Ill):  and 
elsewhere,  A  somewhat  more  detailed  aeeonnt  has  been  given  by  him  of  the  geology  of  a  part  of 
the  western  border  of  the  Selkirks,  resnlting  frr»rn  a  r-eoonnolssanno  made  in  iSSii  and  published 
in  IS'.ii)  In  his  Report  on  a  Portion  of  tho  West  Koolanie  District  (Annual  Report  Geol.  Surv.  Can., 
new  series,  vol.  IV). 


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plateau  rofiion  and  is  based  on  ()])scrvati()ns  inado  on  Koofanio  lake  in  the 
western  flanks  of  the  Sclkirks,  snpplenicnted  by  a  seetion  found  on  and  near 
Adams  and  tlie  Siiuswap  lakes,  altout  1 ")()  miles  to  the  northwest  of  the  first- 
mentioned  locality.  The  lowest  rocks  in  this  column  are  those  referred  to 
the  Arciiean,  the  tliickiu-ss  stated  hein^  merely  that  known  to  occur  on 
Kootanie  lake.  The  rocks  included  in  the  Adams  I^ake  series,  consisting  of 
fi;ray  and  green  schists,  and  forminj;  so  large  a  part  of  the  <'ntire  thickness, 
have  l»een  merely  referred  in  a  general  way  to  the  Paleozoic.  In  their 
typieal  locality  they  appear  to  be  distinctly  traceable  on  their  line  of  strike 
into  contemporaneous  diabase  and  diorite  rocks,  which  are  often  agglom- 
erates, and  pass  into  volcanic  ash  rocks,  where  their  constituents  become 
finer.  The  peculiar  lithological  character  (which,  taken  by  itself,  might  be 
supposed  to  indicate  that  the  rocks  siiould  be  classed  as  upper  parts  of  the 
Archean)  of  these  Adams  T^akf  «chists  is  thus  believed  to  depend  chiefly  on 
the  dynamic  metamorphism  resulting  from  extreme  pressure  which  has 
affected  the  volcanic  components  of  the  Paleozoic,  where  these  have  been 
includeil  in  the  strict  flexures  of  the  mountain  region  of  the  Gold  system. 
No  direct  paleontological  (!vidence  is,  however,  forthcoming  with  respect  to 
the  age  of  the  rocks  of  this  first  column  of  the  table. 

The  third  column  in  the  table  represents  Mr.  McC'onnell's  published  sec- 
tion in  the  Rocky  Mountains  proper,  in  which  certain  horizons,  ranging  up- 
ward from  the  lower  Cambrian,  ai*e  definitely  fixed  by  fossils.  It  was  found, 
in  working  out  the  section  in  this  part  of  the  Tvocky  Mountains,  that  a  consid- 
erable difl'erence  exists  between  the  section  of  the  eastern  as  compared  with 
that  of  the  western  part  of  the  range,  the  pre«ent  width  of  which  (whatever 
that  originally  occupied  by  the  rocks  com[)o8ing  it  may  have  been)  is  about 
sixty  miles  only.  The  particular  feature  of  this  change  which  is  interesting 
in  the  present  connection  is  that  observed  in  the  Castle  Mountain  (Cambrian 
and  Canibro-Siliirian)  group,  which,  although  it  is  on  the  east  essentially  a 
limestone  formation,  is  found  on  the  west  to  consist  in  large  part  of  greenish 
calc-schists  and  greenish  and  redilish  shales  and  slates.'*^  No  granitic  rocks 
or  true  crystalline  schists  are  seen  in  any  part  of  this  section. 

The  .section  rejjresented  by  the  middle  column  in  the  table  is  that  now 
obtained  for  the  Selkirks.  It  occupies,  geograj.  >iically,  as  it  does  in  the  table, 
a  position  intermediate  between  that  of  the  eastern  border  of  the  interior 
plateau  and  that  of  the  Ilocky  Mountains.  In  this,  as  in  the  section  given 
in  the  first  column,  no  horizons  have  yet  been  fixed  paleontologically,  and  the 
position  given  to  the  rocks  therefore  depends  ]>rincipally  on  the  comparison 
of  the  section  with  that  known  in  the  Rocky  Mountains  proper.  It  is  prob- 
able, from  the  composition  and  condition  of  the  rocks,  that  they  may  yet  be 
found  to  hold  fossils:  but  in  the  meantime  it  is  believed  that  the  lithological 


*  Annual  Report  Geol,  Surv.  Can.,  1886,  pp.  24i),  25d. 


170 


(i.    M.    DAWSON — sritlCTIKI':    til'    TIIK    SKI.KIKK     ll.VNdi;. 


ri'H('iiil)lan('<'  ol'  the  ronnutidii.s  to  tiiusc  met  willi  in  i\n'  liucky  MiniiitainH  in 
ill  itsult'.xufiicii'iit  to  t'lmiile  some  imporliiiit  ;;('iu'nil  ("oiicluxioin  to  i)e  iirrived 
Bt  respcclinj,'  tlie  rovkn  of  tiie  Selitirk  niiijje,  wliiie  tlie  uimlo^iy  of  tlio  rockH 
of  the  Scikirks  to  tlioso  of  tiit>  lirsl  section  is  also  such  as  to  afford  some  eliie 
to  till'  ajje  of  tlie  formations  represented  in  it. 

The  Shii/iiviip  Sirlrtt. — 'I'lie  lowest  erystalline,  and  presunuibiy  Arclieun, 
rocks  lar;;ely  represented  in  tlie  western  portion  of  tliis  part  of  tlie  Selkirk 
raiif^o  are  evidently  referalile  to  the  Slmswap  series  of  tiie  lirst  st'ction. 
They  consist  chielly  of  gray  gneisses,  varying  from  nearly  massive  to  quite 
sdiistose,  and  in  the  latter  case  freipiently  having  tlieir  division-phmea 
thickly  covereil  with  glittering  miea.  They  are  both  hornhiendii'  and  mica- 
ceous, hut  the  last-named  mineral  usually  preponderates.  Ortiioelase  is 
H|)pareiitly  the  most  uhuudant  feldspar,  (|uart/.  is  nearly  always  well  repre- 
fienti'd  and  garnets  are  not  infre(|nent.  In  numy  places  nearly  half  the 
entire  mu.ss  of  the  roeks  exposed  consist.s  of  iiitriisivo  or  vein  granite,  with 
pegmatitic  or  gri',ihitic  tcmleneies. 

Thr  NIxconlii/i  Serlen. — Overlying  the  hasal  holo-erystalliiie  series  in  the 
Selkirk  seoiion  is  a  mass  ot  rocks  of  whieh  the  thickness  is  estimated  at 
l."),000  feet.  These  are  dark-."olored  and  generally  hiackish  argiilite-schistft 
nml  ])hyllite8,  representing  variou"}  stages  in  alteration  between  true  nrgil- 
litrs  and  micaceous  schists.  The  rocks  are  usually  rather  finely  fissile,  with 
glo.ssy  and  sometimes  wrinkled  surfaces,  but  often  with  nmch  minute  yet 
visible  mica  on  the  division-planes.  These  planiis  are  in  some  cases  evi- 
dently due  to  cleavage,  but  ai'o  often  true  bedding-plaiu's.  The  roeks  are 
usually  calcareous,  and  fre(pUMitly  hold  tlun  layers  of  da  k-i)lnish  or  black 
impure  limestone,  together  with  occasional  layers  of  dark  (juartzite.  The 
coloration  i.s  evidently  due  to  carbomiceous  matter,  and  pyrites  crystals 
are  very  common  in  certain  zones.  The  only  notable  <liversity  met  with  in 
this  otherwise  liomogeneous  nui.ss  of  rocks  is  fomid  towards  the  base,  where 
(at  the  lower  end  of  Albert  canon)  a  bed  of  pure  blue-gray  crystalliiu'  lime- 
stone thirty  feet  or  more  in  thickness  occurs,  and  a  short  distance  still  lower 
in  the  section,  a  si'ries  of  beds  over  1,0(I(I  feet  in  thickness,  consisting  cbieHy 
of  granular  pale-gray  (juartzites.  The  quartzites  are  sometimes  flaggy  and 
generally  more  or  less  micaceous,  and  are  interbedded  as  well  as  overlain 
ami  underlain  by  blackish  micaceous  argillites  and  layers  of  coar.sely  niica- 
ceous  pale  schists. 

These  rocks  undoubtedly  represent  the  Ni.scoulith  series  of  the  first  column, 
of  which  no  e.N tended  sections  have  yet  been  found  in  the  interior  plateau, 
while  to  the  eastward  they  certainly  corresjiond  in  the  main  with  the  Bow 
liiver  series  of  the  Rocky  Mountains,  for  which  a  thickness  of  ]U,()0<>  feet 
was  there  ascertained,  though  the  base  of  the  series  is  never  exposed  in  the 
Rocky  Mountains. 


l»KFlxiTii>\  (ir  Tin:  ski.kikk   SICUIKS. 


The  Selkirk  Serie*. — Betwci'ii  tlic  ('(iic^'oiii;;  series  iiiul  tlic  next  ovcrlyiiiff 
niOHH  of  l)e(lH  in  tlic  Selkirk  Heetion  no  distinct  line  of  division,  even  of  a 
litholo^riciil  clmriicler,  lui.s  been  oliscrved,  there  lii,'in;r  ii|i|>iirenlly,  on  the 
contriiry,  a  ei)nsidcrai)l(!  tliiukin'Hs  of  passa^'e  hcds,  in  which  the  dark  s<'iii.sts 
of  the  lower  series  alternato  witii  jjray  (|uart/.ite8  and  ;,'ray  >,'''"'*y  •*'<■'>'■"*'•'* 
characteristic  of  the  npf)er  Hcries.  The  «'stiinated  thickness  of  this  overlyinj,' 
Hcries  is  •J.'),()()l)  feet;  and  of  its  rocks  the  lu;;lier  c. Mitral  peakM  of  this  part 
of  the  ran;,'e,  comprising  mounts  Sir  Donald,  .M;ir(Joinild,  Tnpper,  Hermit, 
(,'liei)ps,  Uoss  peak  and  others,  appear  to  he  w  hiiy  eoinposeil.  Litholog- 
icnlly,  it  consists  of  a  j^reat  volume  of  gray  schists  ind  gray  <puirt/.ites,  which 
are  oiicasionally  somewhat  dolomiti(!.  The  ;,irt7,it<  s  jjrolialdy  iire|)onderate, 
and  vary  in  color  from  nearly  white  to  gr  md  greenisli-i:ray,  being  seldom 
dark  in  tint.  They  often,  however,  weather  to  pah  luDwnish  colors  and  pass 
into  conise  grits  and  tine  grained  eonglomera*''s;  and  these  gritri  anil  con- 
glomerates have  become  more  or  U'ss  8cbi«toso  in  structure  as  a  result  of 
pressure,  which  has  also  led  to  the  development  in  tliem  of  much  (iiie  silvery 
nii(ui.  The  schists  vary  in  color  from  pule  neutral-gray  to  L'reenishgray, 
and  from  dull  to  silvery  and  lustrous,  being  in  many  cases  apparently  true 
sericite-Hchists.  They  are  sometimes  wrinkled  and  contorted,  ])articnlarly 
on  the  east  side  of  the  main  synclinal,  where  also  they  occasioinilly  become 
coarsely  micaceous.  To  the  east  of  this  imiin  synclinal  and  beyond  the  great 
fault  shown  in  the  diagrammatic  section  (p.  174)  they  arc  more  crushed 
anil  altered  and  more  highly  micaceous  than  elsewhere,  probably  as  a  result 
of  the  dynamic  conditions  to  which  they  have  been  sul)jected  in  this  region. 

The  rocks  of  this  great  series  ap[)ear  to  re|)re.sent  the  Adams  Lake  serie-s 
to  the  west,  while  they  undoubtedly  correspond,  at  least  in  a  general  way,  to 
the  ('astle  Mountain  group  of  the  Ilocky  ^[ountain  section  on  the  east,  for 
which  group  Mr.  McConuell  ascertained  a  minimum  thickness  of  7,700  feet, 
but  found  reason  to  i)elieve  that  its  total  volume  in  the  western  part  of  the 
range  approached  10,000  feet. 

It  will  be  understood  front  what  has  already  been  said  that  the  line  indi- 
cated between  this  and  the  underlying  series  in  the  Selkirks  is  based  entirely 
on  general  lithological  differences,  while  there  is  every  reason  to  believe 
that  a  plane  of  division  drawn  to  correspond  with  that  between  the  Castle 
Mountain  ;!nd  Bow  lliver  series  in  the  Rocky  Mountains  would  lie  several 
thousand  feet  above  the  recognized  summit  of  the  Nisconlith  series  in  the 
Selkirks.  In  the  Rocky  Mou.  'ains,  the  lower  Cambrian  {Olciielliin)  fauna 
is  known  to  be  common  to  the  lower  part  of  the  Castle  Mountain  and  upi)er 
j)art  of  the  Row  River  series;*  the  sepanuimi  being  there  made  at  the  base 
of  the  distinctly  calcareous  upper  part  of  the  Caml)rian,  while  certain  rather 
characteristic  (unirtz-conglomerates  observed  in  the  upper  part  of  the  Bow 


•This  fiiiiiia  is  kiiiiwii  to  cliaianlerizn  HevernI  ilioiisaiul  feel  of  tlie  Ciistle  Moiintiiiii  .series,  and 
has  been  found  aK  well  about  3,(kK)  feet  down  in  the  upper  part  of  tlie  How  River  series. 


r 


(i.    M.    DAWSON' — S'rnUCTl'llE   OP   TlIK   SELKIHK    UANGE. 


River  series  of  tiie  Rocky  Mountains  are  parnlleled  by  similar  conglomerates 
which  abound  in  the  upper  series  of  the  Selkirks.  No  unconformity  has 
been  observed  between  the  upper  and  the  lower  masses  of  strata  in  either 
j)lace. 

Thougli  in  tlie  Selkirk  section  tlie  lower  of  the  two  great  series  which  have 
been  described  resembles  the  Nisconlith  of  the  interior  plateau  so  closely  as 
to  warrant  extending  the  same  name  to  it,  the  fact  that  the  overlying  mem- 
ber of  the  section  differs  considerably  from  the  Adams  Lake  series  of  the 
interior  plateau,  while  on  the  other  side  it  pn)l)ably  represents  not  only  the 
whole  Castle  ^Fountain  group  but  also  the  upper  part  of  the  Bow  River 
series  of  the  Rocky  Mountains,  renders  necessary  the  application  to  it  of  a 
provisional  distinctive  name.  It  is  therefore  proposed  to  refer  to  this  rock- 
mass  as  the  Selkirk  Series. 

General  Relations  of  the  Cambrian. — Regarded  as  a  whole,  we  find  reason 
to  believe  that  the  Selkirk  section  exhibits  a  great  Cambrian  fornnition 
which  (by  analogy  with  the  Rocky  Mountains)  includes  the  lower  part  of 
the  CambroSilurian  and  reaches  down  from  it  to  and  far  beneath  a  horizon 
at  which  the  Olenelliis  or  lower  Cambrian  fauna  has  been  found,  with  an 
aggregate  tiiickness  of  about  40,00(1  feet. 

The  comparatively  pure  limestones  of  which  the  Cambrian  of  the  eastern 
part  of  the  Rocky  Mountains  is  composed  are  replaced  in  the  western  part 
of  that  range  by  rocks  largely  clastic  in  origin.  This  change  in  lithological 
character  appears  to  continue  and  to  become  still  more  marked  and  to  be 
accompanied  by  increasing  thickness  in  the  Selkirk  range.  ]N[uch  of  the 
clastic  material  is  silicious,  and  the  introduction  of  an  increased  proportion 
of  such  material  nuiy  i)e  explained  by  considering  it  as  a  result  of  approach 
to  the  shore  line  of  Archeau  rocks  on  the  west.  While  the  principal  devel- 
opment of  contemporaneous  volcanic  products,  whether  in  the  Paleozoic, 
Mesozoic  or  Tertiary,  is  conHned  to  a  region  west  of  the  local  Archean  axis, 
the  writer  is  inclined  to  believe  that  a  portion  of  the  remarkable  difference 
found  to  occur  in  the  western  extension  of  the  Cambriau  may  be  due  to  the 
inclusion  in  its  rocks,  on  this  side,  of  volcanic  ash  deposits  or  other  fine- 
grained volcanic  materials,  of  which  the  cornj)usition  was  such  as  to  favor 
the  subsequent  production  of  sericitic  or  sericite-like  schists. 

Speaking  generally,  the  great  Cambrian  formation  of  the  Kocky  Mountain 
and  Selkirk  ranges  shows  many  |)oiuts  of  rcsemblaiice  to  the  Cambrian  and 
so-called  "Algonkian  "  rocks  of  Utah  ami  Nevada,  the  resemblance  being 
particularly  close  in  some  respects  to  the  series  shown  in  the  well-known 
Wasatch  section,  in  which  more  or  lei<s  distinctly  micaceous  schists  are  also 
found.  It  is,  further,  not  at  all  unlike  the  Cambrian  of  Wales,  which,  though 
the  organic  renuiins  are  chieHy  confined  to  some  upper  beds,  has  a  thickness 
of  25,000  feet  and  is  believed  to  exceed  this  in  Shropshire.*     The  provisional 


IXAl'1'LICABILITY   OF   THE   TKini   "AI.GOXKIAX. 


173 


estimate  of  tlie  thickness  of  tlie  Cnnibriun  arrived  at  in  tlie  Selkirks  is,  how- 
ever, greater  than  tiiat  elsewhere  known. 

In  a  late  paper  on  the  stratigraphical  position  of  the  Olenelhis  fauna,* 
Mr.  0.  D.  Walcott  has  suggested  that  the  15ow  River  series  of  the  Canadian 
Koeky  IMouiitains  \m\\  he  regarded  as  "Algonkian."  He  does  not,  liowcver, 
appear  to  have  been  aware  of  the  fact  above  alluded  to,  that  the  Olenellua 
fauna  eharaeterizes  both  the  upper  part  of  this  series  and  the  lower  part  of 
the  Castle  INIountain  gnjup.  With  this  eircumstauce  in  evidence,  together 
with  the  apparently  complete  stratigrapiiical  conformity  of  the  two  series, 
the  writer  cannot  but  regard  it  as  more  in  consonance  with  the  conditions,  so 
far  as  these  are  known,  and  therefore  as  more  j)hilosophical  to  Include,  for 
the  present  at  least,  the  whole  of  this  great  conformable  mass  of  rocks,  to  its 
base,  under  tlie  name  Cambrian.  In  Utah  and  Nevada,  where  ^Ir.  Wal- 
cott's  observations  on  the  western  Caml)rian  have  chiefly  been  made,  it 
seems  that  the  beds  classed  as  "Algonkian"  likewise  in  general  conform- 
ably underlie  those  in  which  the  Oleiicllns  fauna  is  known,  the  conditions 
being  apparently  in  most  cases  similar  to  those  here  described.  On  the 
])r()pricty  of  the  use  of  the  new  term  in  regions  with  which  he  is  not  per.son- 
ally  familiar  the  writer  wishes  to  offer  no  opinion,  but  he  may  take  the 
opportunity  of  stating  that  he  has  met  with  no  rocks  in  Canada  to  which  its 
application  can  at  present  bo  considered  appropriate,  either  in  the  interest 
of  precision  in  the  expression  of  facts  already  a.scertained,  or  because  of 
the  disc(/very  of  heretofore  unrecognized  relations  as  between  the  older 
formations. 

80  far  as  could  bo  definitely  ascertained  in  the  course  of  the  rather 
hasty  examination  upon  which  this  paper  is  based,  the  lowest  beds  of  the 
Cambrian  in  the  Helkirks  (seen  not  far  east  of  Albert  Canon  station)  are 
ill  angular  conformity  to  tlie  Archean  rocks  (seen  to  the  west  of  the  same 
station).  The  actual  junction,  however,  remains  to  be  studied,  as  there  is 
here  a  gap  in  the  section  on  the  lino  of  railway.  In  the  meantime  it  may  be 
stated  that,  notwithstanding  the  appearance  of  conformity,  there  is  reason  to 
believe  llial  a  great  break  in  time  is  here  passed  over;  for,  although  coarse, 
glittering  micaceous  schists  are  found  in  some  parts  of  the  Cambrian,  the 
rocks  of  the  lower  .series  differ  markedly  even  from  these  in  their  completely 
crystalline  character.  The  essential  diversity  in  age  of  the  two  series  is  fur- 
ther shown  by  the  circumstance  that  the  highest  rocks  of  the  Archean  here 
met  with  do  not  include  the  notably  silicious  beds,  the  calcareous  gneisses 
and  the  marbles  which  characterize  the  upper  parts  of  this  ."vstem  n«  ex- 
posed on  Kootanio  lake  ami  near  Shuswap  lake.  It  is  also  found  that  the 
very  numerous  granitic  veins  which  everywhere  cut  the  Archean  rocks  do 
not  enter  the  overlying  Cambrian  strata,  while  a  large  quantity  of  pale-pur- 


•  Am.  .luiirii.  Sel.,  ■iiiil  ser.,  vol.  X.XX  VIII,  ISSl)   ,>.  .Vi. 
XXVI— Hi'1,1,.  litiii..  Soc.  Am,,  Vol,.  ;;,  is'.iii, 


Ir^" 


174 


G.    ^r.    DAWSON' — STRUCTURE   OF   THE   SELKIRK    RAXOE. 


plisli,  sli^flitly  oi)alesceiit  quartz  occurring  in  the  con- 
jrlomcrutes  and  (juartzites  of  the  (.'anibrian  seems 
iin(l()ul)te(lly  to  have  l)een  derived  from  the  denuda- 
tion of  tliese  very  granitic  veins. 

Neiver  Rocks. — On  tlie  eastern  side  of  the  Selkirk 
range  certain  rocks  occur  wliich  are  supposed  to  be 
equivalent  to  the  GraptoUie-heiw'mg  siiales  and  Ilnhj- 
sites  beds  of  the  adjacent  Kocky  Mountains.  As, 
however,  tiie  reference  of  these  beds  must  as  yet  be 
considered  doubtful,  on  account  both  of  the  absence 
of  fossils  and  of  the  unusiuiliy  disturbed  character 
of  this  j)art  of  the  section,  nothing  more  need  here 
be  said  respecting  them. 

The  Devono-Carboniforous,  Carboniferous,  Triassic 
and  Cretaceous  strata  entering  into  the  composition 
of  neighboring  j)arts  of  the  Kocky  Mountains  are  jjuimnsli 
nowhere  seen  in  this  part  of  the  Selkirka. 

Structure. 

Kespecting  the  structural  features  of  the  section 
as  a  whole,  little  need  be  atlded,  as,  in  so  far  as  these 
may  be  considered  to  have  been  determined,  they 
are  rather  simple.  The  western  part  of  the  Seikirjc 
range,  fur  a  wiilth  of  about  seventeen  miles,  is  essen- 
tially composed  of  Archean  and  granitic  rocks,  which, 
it  may  be  added,  are  continued  to  the  west  of  this 
part  of  the  Helkirks  across  the  Columbia  range  for  a 
further  distance  of  about  forty  miles.  These  rocks 
often  li(!  at  low,  undulating  angles,  though  they  are 
occasionally  nuich  contorted.  Above  these,  to  the 
eastward,  is  the  lower  meud)erof  the  Cand)rian  which 
has  been  referred  to  as  the  Nisconlith  series.  This 
forms  a  synclinal,  of  which  the  western  side  lies  at 
a  low  angle,  while  the  eastern  side  i;,  steep,  the  axis 
being  found  near  Illecillewaet  station.  To  the  east 
of  the  synclinal  is  a  rather  sharp  anticlinal,  the 
summit  of  the  dark-c(dored  beds  of  the  Nisconlith 
series  passing  out  of  sight  on  the  east(!rn  side  of  this 
fold  near  the  41Mtli  mile-post  on  the  railway. 

The  next  great  synclinal,  which  coincides  witii  the 
highest  parts  of  the*range,  appears  to  have  a  triiiis- 
vcrse  width  of  about  tliirteen  miles.     The  rocks  con- 


l\. 


*'C. 


a!io)siaADH!iL: 


OROGRAPIiy   OF   TlIK   SKLKIUK   KAXGE. 


17." 


tained  in  it  are  those  of  the  Selkirk  series,  wliieh  is  believed  to  represent 
the  upper  part  of  the  Bow  River  series,  tojrcther  with  the  whole  of  the  Castle 
i\[oiintain  group  of  the  Rocky  IMountain  section.  The  position  of  the  main 
axis  of  tiiis  synclinal  nearly  corresponds  with  Loop  creek,  on  the  railway,  to 
the  west  of  (ilacier  station,  while  a  sul)ordini*te  synclinal  trough  runs  im- 
mediately to  the  east  of  the  same  station  and  nearly  coincides  with  the  actual 
watershed  in  the  pass. 

The  eastern  edge  of  tiiis  synclinal  is  believed  to  be  bounded  by  a  great 
fault,  which  is  supposed  to  cut  the  line  of  i-ailway  near  Cedar  creek  (about  a 
mile  and  a  half  below  Surprise  creek)  and  to  run  on  southward  along  the 
upper  part  of  Beaver  vrtlley.  This  fault  seems  to  have  the  character  of  a 
number  of  those  found  by  jMr.  McConnell  in  an  adjacent  part  of  the  Rocky 
jMountains,  viz.,  that  of  a  fractured  anticlinal,  tiirust  up  on  the  west  side  in 
c()nse(juence  of  ])ressure  acting  from  that  direction. 

To  the  east  of  this  great  fault,  the  section  shown  in  figure  1  must  yet  be 
considered  largely  hypothetical,  as  the  structure  here  becomes  more  compli- 
cated and  there  is  reason  to  suspect  further  extensive  faulting.  There  are, 
however,  grounds  for  the  belief  that,  in  a  wide  additional  synclinal  on  this 
flank  of  the  range,  together  with  tiie  repetition  of  a  great  part  of  the  Selkirk 
group,  still  higher  strata  representing  the  Grap(ol!te-hcnv\ng  shales  and  the 
Ihlijsileii  beds  of  'he  Rocky  Jlountains  are  included.  The  section  ends  on 
the  v^ast  at  the  upper  Columbia  valley,  the  line  of  which  is  coincident  with  an 
important  anticlinal  exposing  rocks  of  tlu;  Castle  Mountain  series,  which  dip 
westward  into  tiio  base  of  the  Selkirk*  and  eastward  into  tlie  opjwsite  base 


of  the  Rockv  Jlountains. 


Thickne.ss. 


If  the  writer  is  correct  in  attributing  a  total  thickness  of  about  40,000  feet 
to  tiie  Cambrian  i  witli  such  part  of  the  Cambro-Silurian  as  may  be  included 
in  the  upper  portion  of  the  Castle  jMountain  group)  of  the  Selkirk  range, 
the  entire  thickiuss  of  the  Paleozoic  obtained  by  adding  to  tliis  that  of  the 
remaining  higher  meml)ers  of  the  adjacent  part  of  the  Rocky  Mountains 
would  be  about  49,000  feet.  Supplementing  this  with  the  thickness  of  the 
Kootanie  and  other  formations  of  the  Cretaceous,  seen  either  in  the  Rocky 
^lountains  oi"  in  the  neighboring  foot-hills  toward  the  east,  we  obtain  a 
total  of  69,000  feet. 

Though,  however,  the  sections  which  give  this  enormous  aggregate  are  all 
(•om[)rised  within  a  distance,  measured  across  the  axis  of  disturbance,  of  little 
more  than  100  miles,  it  is  imrrobable  that  the  whole  of  the  beds  in  their 
maximum  thickness  ever  formed  a  single  column.  The  Cambrian  evidently 
thickens  greatly  at  its  western  nuirgin,  where  not  only  has  the  upper  part  of 
the  I'aleozoic  not  yet  been  found,  but  where  also  there  is  reason  to  believe 


■mm 


170 


G.    M.   DAWSON — STRUCTUIIE   OF   THE   SELKIRK    RANGE. 


that  tlie  very  thick  Cretaceous  formntions  never  extended.  It  must  further 
be  borne  in  mind  that  tiie  adtual  wiiUii  of  100  miles  measured  across  this 
fohled  and  faulted  region  represents  a  zone  of  very  probably  double  this 
width  of  the  surface  as  it  was  antecedent  to  the  great  folding  and  faulting. 
In  this  zone  the  line  of  maximum  sedimentation  a])pears  to  have  moved 
progressively  eastward,  or  away  from  the  local  Archean  laud,  in  the  later 
periods. 

DISCUSSION. 

Dr.  J.  W.  Spknceu:  I  desire  to  again*  claim  priority  for  the  name 
Algonkian,  on  the  ground  that  before  its  publication  I  had  used  the  term 
"Algoncjuiu "  to  designate  an  episode  in  the  (Quaternary  history  of  the 
region  of  the  Great  Lakes. 

Mr.  G.  K.  Grr.ii.KKT:  While  the  two  names  referred  to  by  Dr.  Spencer 
are  based  on  the  same  root,  one  has  the  adjective  form  and  the  other  the 
nominal,  and  (•(  ,  I'usion  is  thus  avoided.  The  simultaneous  and  unobjection- 
able use  of  nouns  and  adjectives  etymologically  identical  for  different  ele- 
ments of  geologic  classihcation  is  illustrated  in  the  case  of  the  "Huron 
siiale  "  and  the  "  Huronian  system,"  and  in  that  of  "  Erie  clay  "  or  "Erie 
shale"  and  the  "  Eriau  period  "  or  system.  The  use  of  "Erie  shale"  for  a 
Paleozoic  fornnition  conflicts  with  the  use  of  "  Erie  clay"  for  a  IMeistocene 
formation,  but  neither  conflicts  with  Sir  William  Dawson's  terra  "Erian." 

*Cf.  Dull,  tieol.  .S')C.  Ani,,  vdI,  1,  1889,  p.  2.)S,  note. 


R'    'JAMES 

p.  O.  BOX  17$ 
*'ANCOUvp«t,  CANADA 

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